Recovery of the components of air



July 1, 1947. y QVA N 2,423,274

RECOVERY OF THE COMPONENTS OF AIR Filed July 6, 1945 INVENTOR 6/4, c'. 1/" M I ATTORNEYS Pat'ented: Jilly Is, 1947' PAT ENT OFF 1 C E 2,4233%v RECOVERY OF THE-COMPONENTS OF AIR Claude Q. Van- Nuys, Greenwich; Conn assignor to Air Reduction Company; Incorporated, New York, N. Y.,. a corporation of' New York Applicatibn FJuly 6, 1945, SerialNot 603,556

I Claim.v

This invention relates to the recoveryor components oil the atmosphere" by liquefaction and rectification of. air and: particularly to' the separation 1 and; recovery of? oxygen off any desired. purity" up to: about 99:6% and a. fraction consisting. of. the. krypton and xenon: present in theatmosphere;

N0 separation of componentsmore volatile than nitrogen is. attempted; these components together" with most of the" argon being combined with the ni trogenwhich: is: separated initthe initial treatsimple and. economical; procedure which permits the continuous'recovery *of'substantially pure oxygen and krypton-xenon. in. a: commercially practicableimanner.

Other objects: and. advantages ofthe invention: will be apparent. as it is better. understood by reference-: to. the: following specification. and;

the accompanying drawing-, whi'ch illustrates dia-- grammatically-an apparatussuitableior the =prac= tice oi" the nriethod',v it being: understood. that I details well. known. in the art are omitted for thepurpose=of:.'clarity-.

- Imcarrying. outxthe invention, air, initially compressed: to a, suitable pressure, for example up' wardto 2'0 atmospheres, and cooled in the. usual interco'olers; and exchangers, is subjected to initiali separation by liquefactionv and rectiflcationrto produce-a an. eiiiuent" consisting principall'y' ofnlitrogen but including components more volatile thaninitrogen and. also-most of; the argon. The eilliient. can: be discharged. to the atmosphere or delivered-tow suitable storage 1' facilities after pass: ing. through therexchangers where its refrigerative' value; is recovered. The liquid product obL-- tained;in:.thexinitiali treatment consists principally" oft oxygen. and. kryptomxenong. although. it may.

carry smallam'ounts of: argon. This liquid'lis sub-i iected to an; auxiliary rectification. with selective condensationiof the effluent which consistsof substantially' pure oxygen. The liquid product of the auxiliary rectification is krypton-xenon; whichmay' be withdrawn. as desired. Theoxygen, afterpassingthrou'ghthe usual exchangers, can be delivered: to. suitablestorage facilities. In

fractions, one consisting of enriched oxygen liquid and the other consisting of liquefied nitrogen; The latter is utilized as a cooling agent in the selective liqueiaction' of the eflluent from the auxiliary rectification and if desired as a portion of the reflux. in the initial separation of the air.

Referringto' the drawing, the initial separation is effected. in a column consisting of upper and lower rectification columns 5 and 6 and an intermediate'conden'ser section I. The rectification sectionsincludethe usualtrays 8 and bubble caps 9. The air, compressed and cooled as hereinbefore described, isintroduced through a pipe l0 andv delivered; through a pipe ll controlled by a valve I21 to a coil I3 a1; the bottom of the rectification section 61 Flowing downwardly over the traysv 8 the liquid is enriched in oxygen. The vapors. risingthrough the trays pass upwardly through tubes I 6 of the condensersection I to a head l1, being subjected to partial. liquefaction therein. The liquid flows backwardly to the trays. The uncondensed residue, consisting substantially of'nitrogen, flows downwardly through the" tubes- L8" in which the nitrogen is liquefied. The liquid nitrogen accumulates in a collector l19 and" is delivered through a pipe ZO-andpressure reducing valve 21 to the top of the rectification section: I, affording the reflux liquid necessary to complete the separation. Enriched oxygen liquid is withdrawn from thebottom of the rectification sectionG' through a pipe 22 controlled by'a valve 23 and'isdelivered through a pipe 24 and pressure reducing valve to an intermediate level of the rectification section 5. The liquids flowing downwardly'through the rectification section 5 are enriched in. oxygen and krypton-xenon and accumulate in: the condenser section I. The effluent, consisting of nitrogen, with more volatile constituentssuchla'sneon. and helium, together with a. considerable proportion of the argon, escapes throughiapipe 26 and may be discharged or delivered to suitable storage. The rectification to effect initial separation can be conducted at any suitablepressures, for example 5 atmospheres absoluteinxthe rectification section 6 and 1 atmosphereabsolute in the rectification section 5.

The liquid from the condenser-section I is withdrawnv through a pipe 21 and flow regulating valve 28 and delivered to an intermediate level order: to :maintain the necessary refrigeration: in thesystem; a portion of the: high pressure'air is diverted touan' auxiliary column. whereit is sulrjected to selective liquefaction to produce two of an auxiliary column 29 having the usual trays 3i) and bubble caps 3|. In flowing downwardly over the trays, the liquid becomes progressively enriched. in krypton xenon, and oxygen vapors rise through thetrays andflnally enter tubes 32 of a condenser section 33 at the top of the column. The tubes are surrounded by liquid nitrogen supplied as hereinafter described. The resulting heat exchange between the liquid and vapors ensures liquefaction of krypton-xenonv in the vapors so that only oxygen escapes through a pipe 34 from a head 35. Minor amounts of impurities may be present in the oxygen, which however can be produced at any desired purity from 95% to 99.6%. The oxygen is delivered through the usual exchangers to suitable storage facilities.

To afford the nitrogen liquid utilized in the condenser section 33, a portion of the high pressure air is diverted through a pipe 36 and delivered to tubes 31 immersed in the liquid which collects at the bottom of the auxiliary column 29. The air, in passing through the tubes, is liquefied selectively, and an enriched oxygen liquid collects below the tubes 31 and is withdrawn through a. pipe 38 and flow regulating valve 39. This liquid joins the liquid in the pipe 24 which is delivered to the rectification section through the pressure reducing valve 25. The residue of the air, consisting substantially of nitrogen, is withdrawn through a pipe 40 and delivered through a flow regulating valve 4| to the tubes 42 of a condenser disposed within the auxiliary column 29 and surrounded by liquid flowing downwardly through the column. The nitrogen is thus liquefied at substantially its initial pressure, i. e., that in pipe 10. It is withdrawn through a pipe 43 and delivered through a .pressure reducing valve 44 to the condenser section 33. A portion of the liquid is diverted through a pipe 45 and valve ,46 to the top of the rectification section 5, thus restoring to the main column an amount of liquid reflux equivalent to the liquid lost by the main column through pipe 21. The nitrogen vaporized in the condenser 33 is delivered through a pipe 41 to the pipe 26, and thus escapes with the nitrogen product of the separation.

The liquid krypton and xenon which accumulates about the tubes 31 at the bottom of the auxiliary column may be withdrawn as desired through a pipe 48 controlled by a valve 49. It may be delivered to any suitable storage facilities.

The operation as described ensures the effective separation of the air into the desired constituents in a continuous and economical manner. All essential refrigeration for the maintenance of the operation is produced effectively by utilizing the air at the initial pressure in the manner described. An ample supply of liquid nitrogen is available to ensure the removal from the oxygen product of substantially all impurities, particularly krypton and xenon, which is accumulated in liquid form and withdrawn as a separate product.

Various changes may be made in the details of the procedure and in the apparatus employed without departing from the invention or sacrificing the advantages thereof.

I claim:

The method of recovering substantially pure oxygen and krypton-xenon simultaneously from the atmosphere by liquefaction and rectification of air, which comprises subjecting a. portion of the air to a primary separation by liquefaction and rectification to produce a gaseous eiiluent consisting of nitrogen, components more volatile than nitrogen, and a substantial part of the argon present in the air and a liquid consisting principally of oxygen and krypton-xenon, subjecting the liquid to an auxiliary rectification'followed by partial condensation of the gaseous eiliuent therefrom by heat exchange with liquid nitrogen to separate krypton-xenon as a, liquid product, providing liquid nitrogen and enriched oxygen liquid by selective condensation of another portion of the air through heat exchange with the krypton-xenon liquid, utilizing a part of the liquid nitrogen so provided in the partial condensation of the gaseous eliiuent from the auxiliary rectification and utilizing the remainder of the liquid nitrogen and the enriched oxygen liquid in the rectification step of the primary separation.

CLAUDE C. VAN NUYS.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 2,040,112 Van Nuys May 12, 1936 2,051,576 Schlitt Aug. 18, 1936 1,963,809 Schuftan June 19, 1934 2,195,987 Gomonet Apr. 2, 1940 

